Data communication and networking notes_Lecture 2 (1).ppt
- 1. 1 Computer Communication & Networks Lecture 2 Introduction to Data Communication http://web.uettaxila.edu.pk/CMS/coeCCNbsSp09/index.asp Waleed Ejaz waleed.ejaz@uettaxila.edu.pk
- 2. 2 Data Communications The term term telecommunication telecommunication means means communication at a distance. The word communication at a distance. The word data data refers to information presented in whatever refers to information presented in whatever form is agreed upon by the parties creating form is agreed upon by the parties creating and using the data. and using the data. Data communications Data communications are are the exchange of data between two devices the exchange of data between two devices via some form of transmission medium such via some form of transmission medium such as a wire cable. as a wire cable.
- 3. 3 Fundamental Characteristics The effectiveness of a data communication system depend on four fundamental characteristics: Delivery Accuracy Timelines Jitter
- 4. 4 Five Components of Data Communication 1. Message 2. Sender 3. Receiver 4. Medium 5. Protocol
- 5. 5 Direction of data flow Simplex Half Duplex Full Duplex
- 6. 6 Networks: key issues Network criteria Performance Throughput Delay Reliability Data transmitted are identical to data received. Measured by the frequency of failure The time it takes a link to recover from a failure Security Protecting data from unauthorized access
- 7. 7 Terminology The throughput or bandwidth of a channel is the number of bits it can transfer per second The latency or delay of a channel is the time that elapses between sending information and the earliest possible reception of it
- 8. 8 Network topologies Topology defines the way hosts are connected to the network
- 9. 9 Network topology issues 1. high throughput (bandwidth) 2. low latency a goal of any topology
- 10. 10 Bandwidth and Latency 1. telecommunications: range of radio frequencies: a range of radio frequencies used in radio or telecommunications transmission and reception 2. computing: communications capacity: the capacity of a communications channel, for example, a connection to the Internet, often measured in bits per second 3. a data transmission rate; the maximum amount of information (bits/second) that can be transmitted along a channel Latency A synonym for delay, is an expression of how much time it takes for transmission from one designated point to another Bandwidth
- 12. 12 Mostly used network topologies mesh star bus ring
- 13. 13 A hybrid topology: a star backbone with three bus networks
- 14. 14 Hierarchical organization of the Internet
- 15. 15 Layering & Protocol Stacks
- 16. 16 What’s a protocol? human protocols: “what’s the time?” “I have a question” introductions … specific msgs sent … specific actions taken when msgs received, or other events network protocols: machines rather than humans all communication activity in Internet governed by protocols
- 17. 17 Protocol protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt a human protocol and a computer network protocol: Hi Hi Got the time? 2:00 TCP connection req. TCP connection reply. Get http://gaia.cs.umass.edu/index.htm <file> time
- 18. 18 Standard Essential in creating and maintaining an open and competitive market for equipment manufacturers Guaranteeing national & international interoperability of data & telecommunication technology & process.
- 19. 19 Layered Tasks An example from the everyday life Hierarchy? Services
- 20. 20 Why layered communication? To reduce complexity of communication task by splitting it into several layered small tasks Functionality of the layers can be changed as long as the service provided to the layer above stays unchanged makes easier maintenance & updating Each layer has its own task Each layer has its own protocol
- 21. 21 Reference Models OSI reference model TCP/IP
- 22. 22 OSI Reference model Open System Interconnection 7 layers 1. Crate a layer when different abstraction is needed 2. Each layer performs a well define function 3. Functions of the layers chosen taking internationally standardized protocols 4. Number of layers – large enough to avoid complexity
- 23. 23 Seven layers of the OSI model
- 24. 24 Exchange using OSI Model
- 25. 25 The interaction between layers in the OSI model
- 26. 26 Issues, to be resolved by the layers Larger bandwidth at lower cost Error correction Flow control Addressing Multiplexing Naming Congestion control Mobility Routing Fragmentation Security ....
- 27. 27 OSI Layers
- 28. 28 Physical layer Transporting bits from one end node to the next - type of the transmission media (twisted-pair, coax, optical fiber, air) - bit representation (voltage levels of logical values) - data rate (speed) - synchronization of bits (time synchronization) physical connection
- 29. 29 The physical layer is responsible for movements of individual bits from one hop (node) to the next. Note
- 30. 30 Data Link layer Transporting frames from one end node to the next one logical connection - framing - physical addressing - flow control - error control - access control
- 31. 31 Data Link layer - hop-to-hop delivery-
- 32. 32 Data Link layer - example-
- 33. 33 The data link layer is responsible for moving frames from one hop (node) to the next. Note
- 34. 34 Readings Chapter 1 (B. A Forouzan) Section 1.1, 1.2, 1.3,1.4 Chapter 2 (B.A Forouzan) Section 2.1, 2.2
- 35. 35